Poly tract infectivity

Vann, W.F. and Jann, K. (1979) Structure and serological specificity of the K13 poly-antigenic polysaccharide (K13 antigen) of urinary tract infective E.coli. Infect. Immun. 25 85-92... 

Predy GN, Goel V, Lovlin R, Donner A, Stitt L, Tapan KB. Efficacy of an extract of North American ginseng containing poly-furanosyl-pyranosyl-saccharides for preventing upper respiratory tract infections a randomized controlled trial. CMAJ 2005 173(9) 1043-1048. 

Figure 3 Structures of the two alternative a chains of meningococcal LOS. The residnes are attached in seqnence by the transferases as shown. Transferases encoded by the IgtA, IgtC, and IgtD genes contain the poly-G tracts and are responsible for the phase variation in LOS. In fact, structure II is made only if IgtA is inactive. At certain stages of meningococcal infections, the chain may further be sialylated.

While the poly (A) sequences do seem to be involved in the transport of mRNA s from the nucleus, this does not seem to be the sole function of the poly (A) tract for example, adenovirus DNA appears to lack a DNA sequence complementary to poly (A) but replicates in the nucleus of the mammalian cell and appears to have a poly (A) tract added to the viral mRNA by host-cell mechanisms for transport of the adenovirus mRNA to the cytoplasm (Philipson et ah, 1971). As with cellular messages, cordycepin blocks both the labeling of the poly (A) tracts and the appearance of adenovirus-specific RNA in the cytoplasm of infected cells (Philipson et ah, 1971). In contrast, vaccinia virus replicates exclusively in the cytoplasm of cells it infects and still contains poly(A) sequences (Kates, 1970). Since no role in transport is involved here, it suggests that some mRNAs may require a poly (A) sequence for proper translation. Further, not all mammalian mRNAs contain poly (A) and still are transported to the cytoplasm for translation. Specifically, the 9 S histone message isolated by Adesnik and Darnell (1972) from HeLa cells lacks any detectable poly (A) sequence of any significant length. These workers have also shown that the exit time of the histone mRNA molecule from the nucleus is shorter than that of other messenger RNA s. 

The picornavims RNAs, which act as mENAs at least initially after infection, also contain, unsurprisingly, a 3 teiminal poly(A) tract in all cases which have been studied. These include ... 

One question that deserves attention is the fact that, at least in the case of some virus-cell systems, viral RNA translation is inhibited preferentially over host mRNA translation, for example, in reovirus-infected L cells (Gupta et al., 1974). An interesting possibility was raised by Nilsen and Baglioni (1979). They showed that, in extracts of interferon-treated cells, VSV mRNA hybridized with poly (U) at its poly (A) tail or EMC RNA hybridized with poly (I) at its poly (C) tract are more rapidly degraded than the corresponding control mRNAs. They proposed that, in infected, interferon-treated cells, activation of the endoribonuclease takes place near the replicative intermediate of RNA viruses, because the dsRNA moiety therein promotes the formation of (2 -5 )oligo (A) in its vicinity. As a result, the viral mRNA portion in the replicative intermediate may be more sensitive to degradation than host mRNA. 

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